In conventional laser fusion cutting, a kerf is melted in a workpiece using a laser beam and the resulting molten material is expelled from the kerf using a cutting gas, such as nitrogen or argon. In addition to the high consumption of cutting gas typically required to produce the necessary gas pressures of up to 20 bar, the supply of the cutting gas is problematic in view of the accessibility at the processing point and also in view of tracking. Accessibility and tracking problems can be of particular concern in so-called remote applications in which the laser beam can cover a wide processing field via a scanner optics device without moving the processing head. DE 102 04 993 A1 proposes to movably mount gas nozzles to scanner optics (laser scanner) and track them through control in dependence on the beam deflection such that the gas flow and the laser beam emitted by the laser scanner are directed to the same area on the workpiece surface. This approach is disadvantageous due to the high level of gas consumption, the existing interference contour of the gas nozzles, the larger dimensions of the processing head, and the added expenses attributed to the integration of control systems. Additionally, the deflection speed of the laser beam can be limited by the maximum travel speed of the attached gas nozzles.
For sublimation cutting in which material is evaporated in the kerf, thereby producing as little molten mass as possible, using laser pulses of high power density (higher than in conventional laser fusion cutting), cutting gas can be omitted since the material vapor in the kerf generates a sufficiently high pressure to expel the molten material from the kerf or from the removal region in an upward and/or downward direction. However, depending on the application, the processing point may need to be shielded via a process gas, such as nitrogen, argon or helium, to protect it against oxidation. Also, sublimation cutting can require high laser power densities such that the removal rates and therefore the cutting depths that can be achieved are limited in practice, in particular for metals. Also, due to the relatively small removal volumes, sublimation cutting of increasingly higher thickness materials can require multiple contour processing.